Classification apparatus



Aug. 20, 1968 Filed April 25. 1966 FIG! D. R. BEUZEVAL 3,397,780

CLASS IFICATION APPARATUS 2 Sheets-Sheet l INVENTOR DOUGLAS ROY BEUZEVAL 4 TI 051E51 1968 D. R. BEUZEVAL 3,397,780

CLASSIFICATION APPARATUS 2 Sheets-Sheet 2 Filed April 25, 1966 INVENTOR DOUGLAS ROY BEUZEVAL FwWJM his ATTORNEYS United States Patent 3,397,780 CLASSIFICATION APPARATUS Douglas R. Beuzeval, Burgess Hill, England, assignor to Buell Engineering Company, Inc., Lebanon, Pa., a corporation of Delaware Filed Apr. 25, 1966, Ser. No. 545,098 Claims priority, application Great Britain, Apr. 27, 1965, 17,723/ 65 8 Claims. (Cl. 209-137) This invention comprises improvements in or relating to classification apparatus by which particulate solid materials are separated according to particle settling velocities.

According to the present invention classification apparatus comprises a chamber, an exhaust duct leading from the top of the chamber, a cascade of vanes or the like extending across the duct and defining spaces afiording outlet paths from the chamber into the exhaust duct, a lateral inlet for the delivery of particulate material in a fluid stream into the chamber in a direction transversely to the cascade of vanes, whereby fluid flowing from the stream into the exhaust duct makes a rapid change of direction thereby to subject the entrained particulate material to inertial separation, a grid-like floor at the bottom of the chamber below the cascade of varies and providing access to a closed collector space, and a concave lateral wall extending from the side of the cascade remote from the lateral inlet towards the adjacent side of the grid for causing a circulation of fluid flowing beyond the cascade of vanes whereby particulate material in the circulatory flow is frictionally retarded by contact with the wall prior to flow of fluid across the grid and whereby any particulate material falling under gravity directly towards the grid is subjected to scrubbing action by the circulatory flow.

The rapid change of direction of the first part of the stream is followed by particles of material, which have low settling velocities and which for convenience may be referred to as lighter particles, whilst other particles do not change direction, so that thereby a separation of particles occurs although this separation is not necessarily absolute in that some lighter particles may be carried with heavier particles which do not follow the rapid directional change, that is particles which have high settling velocities. The frictional retarding efiect of the concave wall is greatest on the heaviest particles in the flow turned by the wall so that these particles have a greater tendency to fall through the floor into the collector space, and thereby classification is further assisted. The scrubbing action causes separation of lighter particles which may be adhering to or drawn along by heavy particles tending to fall directly to the grid.

The classification apparatus of this invention clearly can be of simple construction, and it will preferably have a second concave lateral wall facing the first concave wall and extending from the opposite side of the floor to the lateral inlet so that the latter is at the top of the second concave lateral wall.

The closed collector space may conveniently be in the nature of a hopper which has a valve-controlled bottom outlet and is separated from the circulation chamber by the grid-like floor, the interstices of which are such as to permit the passage of the heavier particles.

The classification apparatus of this invention is also preferably provided with a secondary inlet through which a stream of fluid, preferably substantially clean air, may be directed into the chamber to assist maintenance of the circulation, For instance the secondary stream may be directed along the chamber floor. By varying the strength of the secondary stream, which depends on the volume and velocity of the secondary stream, the average settling velocity of the particles in the heavier particle collector 3,397,780 Patented Aug. 20, 1968 may be varied, an increase in the strength of the secondary stream being accompanied by an increase in the average settling velocity of particles in the heavier particle collector. The stream volume may be controlled by means of, say, a butterfly valve in the secondary inlet, and the velocity may be varied by a flap which may be adjusted to vary the convergence of the final portion of the passage of the secondary inlet.

The vanes or equivalent may be made adjustable to vary their angle of incidence to the line of travel of the fluid from the lateral inlet so that the apparatus may be adjusted to give an optimum efficiency of separation for any particular mix.

One construction of classification apparatus embodying the above features of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic sectional view of the apparatus,

FIG. 2 is an elevation in the direction of arrow 2 on FIG. 1, and

FIG. 3 is a diagrammatic illustration of one form of plant using the classification apparatus.

The classification apparatus comprises a chamber 10 having a pair of concavely-curved lateral walls 11, 12, the radius of curvature of the wall 11 being less than that of the wall 12.

At the upper edge of the wall 11, there is a lateral horizontal duct 13 forming an inlet for a stream of air carrying in it particulate material to be separated. The duct 13 directs the stream towards the upper edge of the wall 12 and thus there is a tendency for air to follow a circulatory path as shown by the arrows 14.

At the top of the chamber and along the upper boundary of the stream entering the chamber from the upper duct 13, there is a cascade of vanes 15, the spaces between which form outlet paths to an outlet duct 16 through which the air leaves the apparatus. The angle at which the vanes 15 are set to the line of travel of the stream from inlet duct 13 causes the outflowing air to partake of a sharp change of direction. This angle may be varied by pivotally supporting the vanes 15 and varying their set angle by an interconnecting linkage. In one form, the vanes are flat strips of metal pivoted at their ends to swing about axes extending along the edges of the strips nearer the chamber 10, their pivots extending externally of the chamber and there carrying radius arms which are interconnected by a common operating bar.

The floor of the chamber is a grid, for instance formed by a series of parallel spaced rods 17, which is below the cascade of vanes 15 and is inclined downwardly from the lower edge of the wall 11 to pass below and in spaced relation to the lower edge of the wall 12. The grid separates the chamber 10 from a collector hopper 18 which is below the chamber. The hopper has a discharge 21 which is controlled by say a rotary seal valve allowing discharge of the material without a continuous flow of air through the discharge.

A secondary air inlet 19 directs the stream of air over the floor of the chamber 10 towards wall 11 and the volume and velocity of the stream are controlled by a butterfly valve 20 in a supply connection 22 of the secondary inlet and by a wall 23 of the portion of the inlet nearest the chamber being formed as a flap pivoted at 24 so as to be swingable towards and away from the opposite wall of the inlet thereby to vary the convergence of the final portion of the inlet.

As the main stream of air carrying the mixed particles enters the chamber from inlet 13, the larger proportion of air is subjected to a rapid change of direction to flow directly to the outlet 16. This subjects the material to inertial separation in that the lighter particles tend to follow the major air flow into the outlet 16, whilst the heavier particles continue in a minor air stream towards wall 12 or fall under gravity towards the floor 17 of the chamber. This minor stream partakes of a circulatory motion in the chamber causing any heavy particles falling towards the floor 17 to be scrubbed by the circulating air and the circulation-borne particles so that adhering lighter particles are detached from the heavier particles and a clean heavy product is obtained. The heaviest particles fall to the floor and pass through it into the hopper 18 whilst any light particles or particles of intermediate settling velocity are carried around in the circulating air until they leave the chamber through the vane cascade 15, or the grid of rods 17. Also larger particles in the circulatory flow tend to be retarded by frictional contact with the wall 12 whereby classification is assisted.

By injecting a controlled secondary stream of air through the inlet 19, the particle size at which separation occurs can be varied. Thus if the strength of the secondary stream is increased, the average settling velocity of particle entering the hopper 18 will be increased as will also be the average settling velocity of particle leaving the apparatus through outlet 16.

The efficiency of separation is determined by the angle of the vanes which may be adjusted to an optimum setting according to the nature of the material being classified and of the desired products.

It will be clear that separation is achieved without moving parts so that the power required for operation depends on the power absorbed by the air blowers. The apparatus is therefore economical.

Referring now to FIG. 3, the classification apparatus as just described may be employed in plant additionally comprising a. main fan which delivers air through ducting 26 to the hopper inlet 28 of a grinding mill 27 so as to entrain the ground particles and carry them along duct 29 to the inlet 13 of the classification apparatus. The outlet duct 16 of this apparatus is connected by ducting 30 to the inlet of a cyclone separator 31 wherein the lighter particles of material are deposited and the cleaned carrier air stream leaves the cyclone 31 through ducting 32 leading to the suction side of the main fan 25 to be recirculated. A branch duct 33 leads from the delivery side of the fan 25 to the secondary air supply connection 22.

I claim:

1. Classification apparatus comprising a chamber, an exhaust duct leading from the top of the chamber, a cascade of vanes extending across the duct and defining spaces afiording outlet paths from the chamber into the exhaust duct, a lateral inlet for the delivery of particulate material in a fluid stream into the chamber in a direction transversely to the cascade of vanes, whereby fluid flowing from the stream into the exhaust duct makes a rapid change of direction thereby to subject the entrained particulate material to inertial separation, a grid-like floor at the bottom of the chamber below the cascade of vanes and providing access to a closed collector space, and a concave lateral wall extending from the side of the cascade of vanes remote from the lateral inlet towards the adjacent side of the grid for causing a circulation of fluid flowing beyond the cascade of vanes whereby particulate material in the circulatory flow is fractionally retarded by contact with the wall prior to flow of fluid across the grid and whereby any particulate material fal l ing under gravity directly towards the grid is subjected to a scrubbing action by the circulatory flow.

2. Apparatus according to claim 1, wherein there is an oppositely-facing concave wall extending from the opposite side of the grid-like floor to the lateral inlet.

3. Apparatus according to claim 1, comprising a sec ondary inlet for directing a stream of fluid into the chamber in a direction to assist maintenance of the said circulation.

4. Apparatus according to claim 3, said secondary inlet directing the fluid along said grid-like floor in the direction of flow of the circulating fluid over it.

5. Apparatus according to claim 4, comprising means to vary the flow through said secondary inlet.

6. Apparatus according to claim 5, said means comprising a butterfly valve in said secondary inlet.

7. Apparatus according to claim 5, said means comprising a flap adjustable to vary the convergence of the final portion of the passage of said secondary inlet.

8. Apparatus according to claim 1, said vanes being adjustable to vary their angle of incidence to the line of travel of the fluid from the lateral inlet.

References Cited UNITED STATES PATENTS 1,484,208 2/ 1924 Davis 209-443 X 3,006,470 10/ 1961 Franken 209132 3,240,335 3/ 1966 Vandenhoeck 209-136 FOREIGN PATENTS 828,125 2/1938 France.

HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

1. CLASSIFICATION APPARATUS COMPRISING A CHAMBER, AN EXHAUST DUCT LEADING FROM THE TOP OF THE CHAMBER, A CASCADE OF VANES EXTENDING ACROSS THE DUCT AND DEFINING SPACES AFFORDING OUTLET PATHS FROM THE CHAMBER INTO THE EXHAUST DUCT, A LATERAL INLET FOR THE DELIVERY OF PARTICULATE MATERIAL IN A FLUID STREAM INTO THE CHAMBER IN A DIRECTION TRANSVERSELY TO THE CASCADE OF VANES, WHEREBY FLUID FLOWING FROM THE STREAM INTO THE EXHAUST DUCT MAKES A RAPID CHAMBE OF DIRECTION THEREBY TO SUBJECT THE ENTRAINED PARTICULATE MATERIAL TO INERTIAL SEPARATION, A GRID-LIKE FLOOR AT THE BOTTOM OF THE CHAMBER BELOW THE CASCADE OF VANES AND PROVIDING ACCESS TO A CLOSED COLLECTOR SPACE, AND A CONCAVE LATERAL WALL EXTENDING FROM THE SIDE OF THE CASCADE OF VANES REMOTE FROM THE LATERAL INLET TOWARDS THE ADJACENT SIDE OF THE GRID FOR CAUSING A CIRCULATION OF FLUID FLOWING BEYOND THE CASCADE OF VANES WHEREBY PARTICOF ULATE MATERIAL IN THE CIRCULATORY FLOW IS FRACTIONALLY RETARDED BY CONTACT WITH THE WALL PRIOR TO FLOW OF FLUID ACROSS THE GRID AND WHEREBY ANY PARTICULATE MATERIAL FALLING UNDER GRAVITY DIRECTLY TOWARDS THE GRID IS SUBJECTED TO A SCRUBBING ACTION BY THE CIRCULATORY FLOW. 